1. Technical Field of the Invention
The present invention relates to a method of manufacturing liquid crystal display devices that are used for the image display panel of a personal computer or a television.
2. Description of Prior Art
A conventional method of manufacturing liquid crystal display device is described below with reference to FIGS. 3 to 5
A liquid crystal display device is constructed as shown in FIG. 3 such that two opposite and spaced substrates, a lower substrate 11 and an upper substrate 12, both being made of a light-transmissive material, are affixed to each other with a UV-curable, photo-polymer adhesive 13, with a liquid crystal material 15 filled in a space between the substrates. The adhesive 13 contains spacers 14 having a 5 .mu.m diameter for keeping the distance between the lower substrate 11 and the upper substrate 12 constant.
In order to dispose the liquid crystal material 15 inside of the adhesive 13 as shown in FIG. 3, one conventional liquid crystal drop method comprises the steps of applying the adhesive 13 on the lower substrate 11 to a thickness of 30 .mu.m at the perimeter (FIG. 4A), dropping the liquid crystal material 15 to an inner side relative to the adhesive 13 (FIG. 4B), superposing the upper substrate 12 above the lower substrate 11 and pressing the substrates until the gap between both substrates becomes 5 .mu.m (FIG. 4C), and curing the adhesive 13 by irradiating ultraviolet light, whereby the liquid crystal display device is completed (FIG. 4D).
The process of affixing the two substrates together in the above conventional method will be described in more detail with reference to FIGS. 5A through 5F.
First, a lower substrate 11, on which an adhesive 13 of UV-curable photo-polymer has been applied to a thickness of 30 .mu.m at the perimeter, after which the resulting cavity has been filled with a liquid crystal material 15, is placed on a table 17 movable in a horizontal direction, and the entire lower surface of the substrate 11 is fixedly held by vacuum suction with a suction-holding mechanism 18 (FIG. 5A). Next, an upper substrate 12 is positioned at a distance opposite the lower substrate 11 and the entire upper surface of the substrate 12 is fixedly held by vacuum suction with a suction-holding mechanism 19 (FIG. 5B). The upper substrate 12 is then lowered so that the distance between the upper substrate 12 and the lower substrate 11 is 1 mm, and the vacuum chamber C is closed (FIG. 5C). Next, the table 17 on which the lower substrate 11 is placed is moved in a horizontal direction for adjusting the positional relationship between the upper substrate 12 and the lower substrate 11, and a vacuum is drawn within the vacuum chamber C (FIG. 5D). The upper substrate 12 is then lowered so that it contacts the adhesive 13 or the liquid crystal material 15 and is further pressed thereon until the distance between the upper and lower substrates becomes 5 .mu.m, whereby the upper substrate 12 is affixed to the lower substrate 11 through the adhesive 13 (FIG. 5E). After that, ultraviolet rays 16 are irradiated for curing the adhesive 13 (FIG. 5F), by which the affixing of upper and lower substrates is completed.
In the above described conventional method, after the positions of the upper substrate 12 and the lower substrate 11 are adjusted relative to each other with the 1 mm spacing therebetween, the upper substrate 12 is lowered nearly 1 mm to contact the adhesive 13 and the liquid crystal material 15, and is further pressed in a vertical direction. There was thus the problem that the upper substrate 12 is sometimes misaligned relative to the lower substrate 11 during the period in which it is lowered toward and pressed onto the lower substrate 11.